Patent GB-848734-A (GB)
Title: Improvements in or relating to pistons
IPC: F16J1/00
Filed: 1958-06-03
Abstract: 848,734. Making pistons; brazing. CORNET, A. June 3, 1958 [June 4, 1957 ; Nov. 26, 1957], No. 17762/58. Classes 83 (2) and 83 (4). [Also in Group XXVI] A piston, e.g. a diesel motor piston, is fabricated from several parts of sheet-metal, preferably sheet steel, and secured by hard-soldering, e.g. copper brazing, an internal stiffening web adapted to support a gudgeon-pin housing being connected both to the head and skirt of the piston. A piston body, Fig. 1, comprising a head 1, a groove-forming portion 2 and a skirt 4 is stamped in one piece, the grooves 3 being formed by axial pressing. Flanges 8 of internal sheet-metal web-plates 6 are brazed to the head 1 and tongues 11 are similarly secured to the skirt. Each web-plate 6 is stamped to form two semi-cylindrical housings 10 for gudgeon-pin bushes, the plates being brazed together face-to-face. In a modification the piston skirt and internal web comprises two semi-cylindrical stamped shells each having a diametrically-situated peripheral flange incorporating semi-cylindrical mountings for the gudgeon-pin bearings. Each shell has an upper portion of reduced diameter and a false head which on assembly of the piston receives a grooved sleeve and a disc, respectively, the latter constituting the head proper of the piston. In assembly of the shells, the peripheral flanges are first brazed together face-to-face and are also brazed to the skirt, the grooved sleeve and disc then being brazed on. In another modification, Fig. 7, the skirt 21 is formed from a mild steel sheet tube having a neck portion 22 to receive a stamped cap 28 forming the head of the piston and carrying the ring-grooves 29, 30 which are machined from the stamping. The cap is brazed in position utilizing a copper ring 24 located in a throat 23. Bosses 25 stamped in the skirt receive sleeves 26 which form gudgeonpin bearings, the inner ends of the sleeves 26 being supported by perforated web-plates 31 which are flanged at 32 to receive the sleeves and are also flanged at 33 and 34 for attachment to the head and the skirt respectively. In all cases the surfaces to be joined are covered with copper prior to assembly after which brazing is carried out in a kiln having a reducing or neutral atmosphere, e.g. hydrogen, at a temperature higher than the melting-point of copper. After brazing the pistons are ground and electrolytically treated. In another modification the skirt and head portion are deepdrawn in one piece and ring-grooves embossed afterwards (Fig. 9, not shown). In a further modification the skirt and a false head are formed from a deep-drawn cylinder with a reduced end to which is brazed a head proper integral with a ring-groove forming portion (Fig. 10, not shown). Alternatively, instead of an integral head unit a head disc and separate groove-defining rings may be brazed to the deepdrawn body. Sodium may be trapped between the head proper and the false head for cooling purposes. Finally a plain tubular skirt shorter than the piston may have an integral head and groove-forming portion brazed on to its end. (Fig. 12, not shown). Parts of the piston may be of different metal from the body.